The present invention relates to a method of producing cyclopentene.
Cyclopentene is useful for example, as a raw material for producing cyclic aldehydes, alcohols and chlorinated compounds, and also as fuel. Recently cyclopentene has been used as a monomer which is polymerized to a high molecular weight polymer. However, the amount of cyclopentene available on the commercial market is so small and the cost thereof is so expensive that use thereof in industrial quantities is unrealistic. There are other reasons for its lack of widespread industrial use. For example, there have been many difficulties encountered in the production of cyclopentene such as during thermal depolymerization of dicyclopentadiene, during selective hydrogenation of cyclopentadiene monomer and during purification of hydrogenated cyclopentene. There is yet no known method which combines these processes into a smooth and economical procedure to produce substantially pure cyclopentene from dicyclopentadiene.
To combine thermal decomposition of dicyclopentadiene and hydrogenation of cyclopentadiene, many problems arise due to the thermal instability of cyclopentadiene monomer. Accordingly, after thermal decomposition of dicyclopentadiene, it is necessary to send the diene monomer to a hydrogenation zone as soon as possible after a quick purification of the monomer. Moreover to prevent dimerization of the monomer, it is necessary to prevent exposure thereof to pressure or to heat before the hydrogenation.
One of the important problems to be solved in the hydrogenation of cyclopentadiene is the decrease of catalytic activity and concurrent decrease of catalytic life time by the adsorption of impurities of high boiling point contained in cyclopentadiene, such as dicyclopentadiene, co-dimers of cyclopentadiene and isoprene or pentadiene, etc.